There is http://www.olegkikin.com/md5game/ http://www.olegkikin.com/md5game/ on which I wasted some GPU cycles many years ago. It uses a very silly metric for p

There is http://www.olegkikin.com/md5game/ http://www.olegkikin.com/md5game/ on which I wasted some GPU cycles many years ago. It uses a very silly metric for progress though. Finding a longer substring that matches doesn't bring you closer to finding MD5(x) = x. It was a fun problem to try out some crypto bruteforcing on the GPU though. I don't think any of the known weaknesses of MD5 would help you in finding MD5(x) = x.